Misoperation Reduction and Fault Detection/Localization by Distributed Signal Analysis
Protective relay equipment in an electric grid substation exists to protect the electric distribution grid from overload conditions and, importantly, to ensure that dangerous fault conditions are promptly de-energized, preserving the safety of life, property, and infrastructure. But, the increasing presence of distributed energy resources, including solar photovoltaic systems, means that a substation is no longer the sole source of energy for the distribution grid. This can reduce fault currents to levels below the set-points of the substation protection relaying equipment, resulting in failure-to-trip misoperation and leaving dangerous faults energized. In addition, other types of faults, such as downed power lines that do not draw large amounts of current, may go undetected at the substation and remain a threat to life, property, and infrastructure. Consequently, an improved method of fault detection and relay notification is urgently needed and is being addressed under the reported project, “Misoperation Reduction and Fault Detection/Localization by Distributed Signal Analysis”. The proposed system for improving fault detection is comprised of two, principal, computational elements, a remote analytics device (RAD) and a substation processing system (SPS). RADs will be installed on the low voltage side of distribution transformers. In addition to supporting communications with other RADs and between individual RADs and the SPS, RADs will transmit engineered waveforms onto the grid that will enable three capabilities that are critical to the operation of the system. The capabilities are: 1) enhanced detection of faults, executed in the service area; 2) identification of the particular feeder protection relaying equipment to which information about a detected fault is relevant, and; 3) cyber-secure communication of the detection alert/information to the substation, where it will be used by the identified protection relay to de-energize the circuit that is providing energy to the fault, avoiding misoperation. The large majority of the work effort was focused on research and development of the mathematical, computer algorithms needed to achieve these three capabilities. Physical testing was conducted using two laboratory-based, surrogate grids and an operating, commercial, electric grid. A transmitter that Elintrix previously constructed to inject signals onto both surrogate and commercial grids was programmed with new, engineered, grid-interrogation and communications signals and operated in both laboratory and field test environments. A prototype SPS was installed at an Anza Electric Cooperative (AEC) substation that supplied four distribution grid feeders, each feeder comprised of three, energized conductors. All 12 feeder-conductors were monitored using split-core current-transformers (CTs) installed on the output leads of the AEC feeder-protection CTs. This method provides non-contact extraction of signals from the substation CTs. The signals arriving from a field-based transmitter were received at the substation and recovered from split-core CTs. The received signals were digitized, stored and post-processed onsite. Prior to testing on-grid, algorithms were validated in the laboratory, using two, surrogate grids that were configured to mimic the Anza grid and system installation. The transmitter and receiving equipment was identical in all tests. Elintrix has been advancing a patented algorithm that performs a comparative analysis of the direction of signal current in each conductor and identifies the feeder/phase over which a message has been transmitted to the substation. Work performed in the current project significantly improved the robustness and reliability of the computational methods, successfully achieving the project goal of minimizing the degree of uncertainty previously observed. On a surrogate grid, a simulated arcing fault was introduced by placing neon lamps between a conductor designated as A-phase, and the neutral. The ionized gas formed a conductive path between the conductors. Engineered signals were transmitted and, simultaneously, received at monitored transformers. The tests demonstrated that cooperative operation of RADs is viable means of detecting short-circuit faults to ground, providing the foundation of the second of the three capabilities required by the system. A signal-based method of enhancing the cyber security of transmitted fault-alerts was researched, implemented and used to successfully send cyber-secure messages over the Anza grid, providing the foundation of the third of the three capabilities required by the envisioned, integrated system. The method operates on the spectrum of the signal to be transmitted. The further spectral operations are conducted on the received signal, resulting in recovery of the transmitted data. The project was advanced with the support of Anza Electric Cooperative (Anza, CA) and Schweitzer Engineering Laboratories (Pullman, WA).
- Research Organization:
- Elintrix
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0019917
- OSTI ID:
- 1604523
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- DOE-Elintrix-19917
- Country of Publication:
- United States
- Language:
- English
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